Starter location on 1997 e350 super duty class c?

Did you first try starting it in neutral as well as park? These safety switches do go bad.

I agree with what Dr.Quick said except that before I did anything else, I'd get someone to turn the ignition to the start position and hold it there, and, assuming there's no response from the starter, take something like a small hammer or crescent wrench and lightly but firmly rap the solenoid next to the battery and maybe you'll get a response. If it works, replace that solenoid with a good quality brand name one. I had the same problem on my Ford E350 van.

Yes two solenoids on these fords with PMGR starters. The one on the starter is "wired" with permanent jumpers where we're used to seeing wiring. So, when that fender mounted solenoid sends current down the cable, it will crank without further input.
My neighbor recently had a starter failure, and it took replacing both starter (with onboard solenoid) and the fender mounted solenoid as well.
I think the damage arose from a friend of the neighbor trying to start it on a very low chassis battery. If the starter's dogging on a low battery, do something about the battery before continuing.

Ford trucks usually have two solenoids. One on the starter, which if you got a new starter should be new. Second one is usually on the inside wheel well close to the battery. I would try using a fairly heavy jumper wire at the second solenoid, from the wire that goes to starter solenoid to positive battery terminal. If engine cranks then that solenoid is bad. If it does not crank, then something may be wired wrong at starter.

"it passed the test a couple of times but then it started to fail"

Could you elaborate on this a little? Where was the starter when it "started to fail"?

Did it test OK on the bench but fail to work on the rig?

Starters that work on the bench have every chance of not working at all when installed in the vehicle. The electricity cannot pass through a bad connection i.e. it will spin OK at 30 amperes of free-spin, then play possum when it tries to consume 200 amperes on the engine. Got it?

The PM (permanent magnet) starters are infamous for eventually wearing carbon brushes down until the point "They Almost Work". The brush copper leads are spot welded onto the steel brush mounting plate so the whole shebang comes as an assembly.

Auto Parts store rebuilt starters are woefully rebuilt. When I had to rebuild an auto parts store rebuilt starter 3/4'ers of the parts were tossed over my right shoulder into a dumpster.

Ford genuine parts (remanufactured) are rebuilt correctly. Ford isn't afraid to stick a brand new armature or drive end housing in a reman, whereas an el-cheapo rebuilder will patch, cobble, and pound parts to save money. Yes the Ford reman will cost more. I always weigh the savings of an El Cheapo versus having a premature el cheapo failure happen during a driving rainstorm.

My "money" is on your starter having worn-out brushes. They get stuck and carbon "goo" glues the brush to the steel brush holding clip.

solenoid on the passenger side fender well under the hood is bad. Just replaced one on the farm truck. Watch how it comes off to put the new one back on in the same position

Starter solenoid would be my guess. You need to verify that your battery is good, also. Not all new batteries have a complete charge. Have you had a lot of wet weather recently?

I found the starter, it was underneath the passenger side tied into the transmission. I removed it and took it to get tested and at first it passed the test a couple of times but then it started to fail. So I bought a new one and replaced it. Once I replaced it and wired it as the previous one had been, I still get nothing. The first try it clicked once after that just nothing, no power at all when I turn the key. So I installed a new battery which I should not have as my old one was technically good but being stupid I chose to, then the starter, now what? The solenoid next to the battery attached to the wall? The alternator? The RV had run fine the last time I drove it, it had been parked in my drive way plugged in, I unplugged it to move it out of the drive way and after a couple of days, it would not do anything. Any suggestions?

Not to judge, but if you can't find the starter, I WOULD STRONGLY suggest you have a mechanic replace it.

Jim

It's a PMGR (Permanent Magnet Gear Reduction) starter. The cable from the Under-Hood Solenoid powers the Solenoid on the Starter Motor. That Solenoid powers the Starter and engages the Drive. In a GM application the battery cable goes right to the solenoid on the Starter and that Solenoid is fired off from the Start Position of the Ignition Switch. So in Ford V10, there are truly TWO solenoids.